Decrypt String from Alphabet to Integer Mapping

class Solution:
    def freqAlphabets(self, s: str) -> str:
        element=[]
        stack=[]
        for letter in s:
            if letter!="#":
                stack.append(letter)
            else:
                num=""
                for i in range(2): 
                    num += stack.pop()
                stack.append(int(num[::-1]))     
        ans=""
        for i in stack: 
            ans+=chr((int(i)+96))
        return ans